Diffusion weighted magnetic resonance imaging in stroke

Diffusion weighted magnetic resonance imaging has evolved from an esoteric laboratory experiment to a critical aspect of routine clinical care of the patient presenting with symptoms suspicious of acute ischemic stroke. The purpose of this article is to review the basis of diffusion weighted imaging (DWI), to consider its application in acute stroke and to recognize potential pitfalls and stroke mimics that might be encountered. Included in the discussion are comments on the elimination of 'T2 shine through' phenomena as well as construction of pixel-by-pixel maps of the apparent diffusion coefficient (ADC). Furthermore, discussion of techniques such as parallel imaging (using SENSE) and PROPELLER sequences will be introduced as methods potentially allowing DWI to be utilized in areas usually associated with prohibitive susceptibility artifact (e.g. the base of the brain). Finally, the concept of interventional therapeutic approaches to salvaging ischemic tissue is introduced, both in terms of the ischemic penumbra (defined by a diffusion/perfusion mismatch) and also in terms of the potential reversibility of the diffusion-weighted hyperintensity, associated with the lesion core.